Soil alters seedling establishment responses to climate.

Ecologists expect species and biomes to shift poleward and upward with climate change, but non-climatic factors complicate these predictions. In mountains, forests are expected to expand upward along climate gradients into subalpine/alpine meadows, while meadows expand upward onto bare ground. However, soils also vary across elevation, with bare soil above the meadows potentially poorer for plant establishment. Poor soil might constrain expansion at meadows' upper edges, while rich meadow soil might facilitate contraction at lower edges by promoting tree establishment. We assessed climate and soil effects on establishment by transplanting soil and seedlings of meadow and tree species across climate gradients on Mount Rainier. There were considerable interspecific differences, but some generalisations emerged. Survival often declined with earlier snow disappearance, with somewhat smaller declines in meadow soil. Size often increased with earlier snow disappearance, with larger increases in meadow soil. Thus, soil patterns may complicate range shifts.